title: A general scavenging rate constant for reaction of hydroxyl radical with organic carbon in atmospheric waters.
abstract: Hydroxyl radical (OH) is an important oxidant in atmospheric aqueous phases such as cloud and fog drops and water-containing aerosol particles. We find that numerical models nearly always overestimate aqueous hydroxyl radical concentrations because they overpredict its rate of formation and, more significantly, underpredict its sinks. To address this latter point, we examined OH sinks in atmospheric drops and aqueous particles using both new samples and an analysis of published data. Although the molecular composition of organic carbon, the dominant sink of OH, is extremely complex and poorly constrained, this sink behaves very similarly in different atmospheric waters and even in surface waters. Thus, the sink for aqueous OH can be estimated as the concentration of dissolved organic carbon multiplied by a general scavenging rate constant [kC,OH = (3.8 ± 1.9) × 10(8) L (mol C)(-1) s(-1)], a simple process that should significantly improve estimates of OH concentrations in atmospheric drops and aqueous particles.
authors.affiliation: Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus , 1 Senbaru Nishihara-cho, Okinawa 903-0213, Japan. arakakit@sci.u-ryukyu.ac.jp
authors.forename: Takemitsu
authors.initials: T
authors.lastname: Arakaki
authors.forename: Cort
authors.initials: C
authors.lastname: Anastasio
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kuroki
authors.forename: Hitomi
authors.initials: H
authors.lastname: Nakajima
authors.forename: Kouichirou
authors.initials: K
authors.lastname: Okada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kotani
authors.forename: Daishi
authors.initials: D
authors.lastname: Handa
authors.forename: Sotaro
authors.initials: S
authors.lastname: Azechi
authors.forename: Taro
authors.initials: T
authors.lastname: Kimura
authors.forename: Ai
authors.initials: A
authors.lastname: Tsuhako
authors.forename: Youichi
authors.initials: Y
authors.lastname: Miyagi
mesh_terms: D001272:Atmosphere; D002244:Carbon / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D014867:Water / Q000737:chemistry*
chemical_list: D016166:Free Radical Scavengers; D014867:Water; D017665:Hydroxyl Radical; D002244:Carbon